Altered cardiac-coronary coupling relates to abnormal fractional flow reserve without flow limitation after percutaneous coronary interventions

A significant proportion of stenoses have an abnormal fractional flow reserve (FFR) after angiographically successful percutaneous coronary intervention (PCI), which is traditionally attributed to differences in coronary flow velocity reserve (CFVR) or hyperemic microvascular resistance (hMR). This study investigated the mechanisms underlying residual low FFR despite good angiographic results and normalized hyperemic stenosis resistance (hSR) using wave-intensity analysis (WIA), which evaluates phasic characteristics of cardiac-coronary coupling. Sixty-three vessels from patients who underwent PCI for stable intermediate stenoses were included. Peri-PCI characteristics of conventional and WIA parameters were assessed. Ten (16%) vessels exhibited residual low FFR (≤0.8) despite normalized hSR (<0.8), without significant differences in hyperemic flow (velocity) (hAPV), CFVR, or hMR compared with concordant normal FFR-hSR group (p > 0.05). WIA revealed a significantly slower (peak-time of backward expansion wave, tBEWpeak = 20% ± 6% vs. 29% ± 17% of expansion period, p = 0.005) and weaker (BEWpeak = 10.1 ± 8.9 vs. 15.8 ± 11.4 10.kW.m-2.s-2, p = 0.045) impact of microvascular suction responsible for diastolic coronary filling during hyperemia in the low FFR group, despite comparable pre-PCI characteristics. Residual low FFR after PCI may reflect altered cardiac-coronary coupling without limitation of flow or vasodilator capacity when the blunted impact of accelerating wave energy flux with delayed coronary filling fails to sustain distal pressure. The influence of cardiac-coronary coupling on post-PCI FFR warrants further investigation.